Mobile communication system, multicarrier cdma transmitter, and multicarrier cdma receiver

ABSTRACT

A transmitting apparatus adds a common pilot symbol and known series for each data slot of a subcarrier group. A receiving apparatus combines SIR calculation values obtained for each subcarrier group, and averages the SIR calculation values. Based on this, it is possible to obtain a high-precision SIR calculation value even when there is a level fluctuation such as shadowing.

TECHNICAL FIELD

[0001] The present invention relates to a mobile communication systemthat employs a multicarrier CDMA, a multicarrier CDMA transmittingapparatus (hereinafter, “transmitting apparatus”), and a multicarrierCDMA (Code Division Multiple Access) receiving apparatus (hereinafter,“receiving apparatus”). The present invention relates, moreparticularly, to a transmitting apparatus and a receiving apparatus thatare used in a frequency selective fading transmission line.

BACKGROUND ART

[0002] A conventional mobile communication system that employs amulticarrier CDMA is explained below. Transmitting and receivingapparatuses of a mobile communication system according to a multipleaccess system using a multicarrier CDMA system are described in, forexample, “Comparison of characteristics between the SC (SingleCarrier)/DS (Direct Spread)-CDMA, MC (Multi Carrier)/DS-CDMA, andMC-CDMA systems in the down link broadband radio packet transmission,The Institute of Electronics, Information and Communication Engineers,Technical Report of IEICE RCS99-130, pp. 0.63-70, October 1999”, and“Overview of Multicarrier CDMA, IEEE Communications Magazine, pp.126-133, December, 1997”.

[0003]FIG. 14 shows a structure of the conventional multicarrier CDMAtransmitting apparatus described in the above literatures. In FIG. 14, areference numeral 201 denotes a serial to parallel converter (S/P),202-1, 202-2, . . . , and 202-n denote a first, a second, . . ., and anN_(scg) (=n)-th subcarrier group modulation processors respectively,203-1, 203-2, . . . , and 203-n denote multiplexers respectively, 204denotes an inverse Fourier transform calculator, 205 denotes a guardinterval (GI) adder, 206 denotes a frequency converter, and 207 denotesan antenna. In the subcarrier group modulation processors 202-1, 202-2,. . . , and 202-n, reference numerals 211-1, 211-2, . . . , and 211-ndenote slot generators respectively, 212-1, 212-2, . . . , and 212-ndenote copying sections respectively, 213-1, 213-2, . . . , and 213-kdenote information modulators respectively, and 214-1, 214-2, . . . ,and 214-n denote spread spectrum sections respectively.

[0004]FIG. 15 shows a structure of the conventional multicarrier CDMAreceiving apparatus described in the above literatures. In FIG. 15, areference numeral 301 denotes an antenna, 302 denotes a frequencyconverter, 303 denotes a guard interval (GI) remover, 304 denotes aFourier transform calculator, 305-1, 305-2, 305-3, . . . , and 305-mdenote common pilot extractors respectively, 306 denotes a by-subcarrierchannel estimator, 307 denotes a delay unit, 308-1, 308-2, 308-3, . . ., and 308-m denote fading compensating sections respectively, 309denotes an inverse spread spectrum section, 310 denotes a parallel toserial converter (P/S), and 311 denotes a data deciding section.

[0005] The operations of the conventional multicarrier CDMA transmittingand receiving apparatuses are explained below. Data transmission andreception between a base station and a plurality of terminals isassumed.

[0006] First, the operation of the transmitting apparatus is explained.Transmission data to be transmitted to an optional terminal is input tothe serial to parallel converter 201, which converts the data intoparallel data of a parallel number N_(scg) (that is, a predeterminedinteger). The parallel data reach the subcarrier group modulationprocessors 202-1 to 202-n respectively. All of the first to theN_(scg)-th subcarrier group modulation processors carry out the samesignal processing for each subcarrier group. Therefore, the operation ofthe first subcarrier group modulation processor 202-1 is explained here,and the explanation of the operation of the rest of the subcarrier groupmodulation processors is omitted.

[0007] Of the parallel data output from the serial to parallel converter201, the first data series is input to the subcarrier group modulationprocessor 202-1. The slot generator 211-1 divides the received dataseries into N_(data), and adds a common pilot symbol to the header ofeach of the divided data, thereby to prepare a frame of one data slot orN data slots. FIG. 16 shows a frame format of a subcarrier unit. Asshown in this drawing, the data slot consists of a pilot symbol portion(that is, a known series), and a data portion.

[0008] The copying section 212-1 receives the data slot of the firstsubcarrier group, copies the frame by a predetermined number ofsubcarriers N_(sub) (=m), and prepares the data slots of the N_(sub)subcarriers. FIG. 17 shows in detail a structure of, for example, thecopying section 212-1. The copying section 212-1 outputs the N_(sub)data slots to the information modulator 213-1. Other copying sectionshave structure similar to that of the copying section 212-1.

[0009]FIG. 18 shows in detail a structure of, for example, theinformation modulator 213-1. In FIG. 18, reference numerals 221-1,221-2, . . . , and 221-m denote QPSK modulators respectively. Theinformation modulator 213-1 receives the N_(sub) data slots, and theQPSK modulators 221-1 to 221-m carry out QPSK modulation of thecorresponding data slots, thereby to prepare N_(sub)information-modulated subcarrier signals. The information modulator213-1 outputs the N_(sub) information-modulated subcarrier signals tothe spread spectrum section 214-1. Other information modulators havestructure similar to that of the information modulator 213-1.

[0010]FIG. 19 shows in detail a structure of, for example, the spreadspectrum section 214-1. In FIG. 19, a reference numeral 222 denotes aspread spectrum code generator, and 223-1, 223-2, . . . , and 223-mdenote multipliers respectively. The spread spectrum section 214-1spreads the spectrum of the N_(sub) information-modulated subcarriersignals respectively by using mutually orthogonal spread spectrum codes(which are expressed as ±1) given in advance in a plurality of terminalsor other transmission channels. More specifically, the spread spectrumsection 214-1 multiplies the N_(sub) information-modulated subcarriersignals by each spread spectrum code that is output from the spreadspectrum code generator 222. For the spread spectrum codes, orthogonalcodes of Walsh codes are generally used. The spread spectrum section214-1 outputs the N_(sub) subcarrier signals after the spread spectrumto the multiplexer 203-1. Other spread spectrum sections have structuresimilar to that of the spread spectrum section 214-1.

[0011] The multiplexer 203-1 receives the N_(sub) subcarrier signalsafter the spread spectrum, multiplexes these subcarrier signals (thatis, transmission signals to be transmitted to the terminals), andoutputs the multiplexed subcarrier signals to the inverse Fouriertransform calculator 204. At this time, the inverse Fourier transformcalculator 204 receives the inputs of all the N_(scg)×N_(sub) (=N_(c))subcarrier signals, which includes the multiplexed subcarrier signalsobtained from the multiplexers 203-2 to 203-n, in addition to the inputfrom the multiplexer 203-1. Other multiplexers have functions similar tothat of the multiplexer 203-1.

[0012] The inverse Fourier transform calculator 204 calculates inverseFourier transform of the subcarrier signals received, and outputs theresultant inverse Fourier-transformed signals to the guard intervaladder 205.

[0013]FIG. 20 explains how the guard interval adder 205 adds the guardintervals. The inverse Fourier-transformed signals output from theFourier transform calculator 204 are continuous signals of symbols. Theguard interval adder 205 copies a portion at the end of theFourier-transformed signal of each symbol corresponding to a timeτ_(GI), and adds that portion of the signal to the header of the signalsfor that symbol. The guard interval adder 205 outputs the guardinterval-added signals to the frequency converter 206. In general,τ_(GI) is set larger than the spread of delayed waves on transmissionlines, that is, τ_(d), shown in FIG. 21. FIG. 21 shows one example ofimpulse responses on frequency selective fading transmission lines. Aswaves are reflected, diffracted, and scattered by the surroundingbuildings and topography, these waves (that is, multi-path waves) arrivein the mobile communication system after passing through a plurality oftransmission lines, and these waves interfere with each other (that is,frequency selective fading).

[0014] The frequency converter 206 carries out a predetermined frequencyconversion processing to the received guard interval-added signals, andoutputs the frequency-converted signals to the radio communicationtransmission lines via the antenna 207. FIG. 22 shows modulation signalson the frequency axis when N_(scg) is equal to four and N_(sub) is equalto eight, for example.

[0015] The operations of the receiving apparatus will be explained nextwith reference to FIG. 15. The frequency converter 302 receives, via theantenna 301, the signals influenced by the frequency selective fading onthe radio communication lines, and converts these signals into basebandsignals. The frequency converter 302 outputs the baseband signals to theguard interval remover 303.

[0016] The guard interval remover 303 removes the guard intervals fromthe received baseband signals, and generates the continuous signals ofsymbols (refer to the upper portion in FIG. 20). The guard intervalremover 303 outputs the signals generated to the Fourier transformcalculator 304.

[0017] The Fourier transform calculator 304 calculates Fourier transformof the signals received, and generates N_(scg)×N_(sub) (=N_(c))subcarrier signals. The Fourier transform calculator 304 outputs all thesubcarrier signals to the delay unit 307, and also outputs thesubcarrier signal of each subcarrier to a corresponding one of thecommon pilot extractors 305-1 to 305-m.

[0018] The common pilot extractors 305-1 to 305-m extract common pilotportions from the received subcarrier signals respectively. Theby-subcarrier channel estimator 306 adds in-phase channel estimatevalues of adjacent three subcarriers, thereby to obtain the channelestimate value of each subcarrier after suppressing noise component. Theby-subcarrier channel estimator 306 outputs the channel estimate valueof each subcarrier to the fading compensating sections 308-1 to 308-m insubcarrier unit.

[0019] On the other hand, the delay unit 307 receives eachFourier-transformed subcarrier signal, and delays each signal to adjustdelays due to the processing in the common pilot extractors 305-1 to305-m and the processing in the by-subcarrier channel estimator 306. Thedelay unit 307 outputs the respective delayed subcarrier signals to thefading compensating sections 308-1 to 308-m.

[0020]FIG. 23 shows a structure of, for example, the fading compensatingsection 308-1. In FIG. 23, a reference numeral 321 denotes a multiplier,and 322 denotes a complex conjugate number calculator. The complexconjugate number calculator 322 receives the channel estimate value insubcarrier unit, and calculates a complex conjugate number of theestimate value. The multiplier 321 multiplies the received subcarriersignal by the calculated complex conjugate number, and outputs thefading-compensated subcarrier signal as the result of themultiplication. The multiplier 321 outputs the fading-compensatedsubcarrier signal to the inverse spread spectrum section 309. Otherfading compensating sections have structure similar to that of thefading compensating section 308-1.

[0021]FIG. 24 shows a structure of the inverse spread spectrum section309. In FIG. 24, a reference numeral 323 denotes an inverse spreadspectrum code generator, 324-1, 324-2, . . . , and 324-m denotemultipliers, and 325 denotes a combiner. For example, N_(sub) subcarriersignals corresponding to each subcarrier group shown in FIG. 22 arehandled as one unit of processing, and N_(sub) subcarrier signals areinput to each of the multipliers 324-1 to 324-m. Each of the multipliers324-1 to 324-m multiplies the N_(sub) subcarrier signals by the inversespread spectrum code (which is the same as the spread spectrum code andwhich can be expressed as ±1) that is output from the inverse spreadspectrum code generator 323. The combiner 325 combines the receivedinversely-spread N_(sub) subcarrier signals, and generates an inversespread spectrum signal corresponding to the subcarrier group signals asthe result of the combining. The combiner 325 outputs the frequencyinversely-spread signal to the parallel to serial converter 310.

[0022] The parallel to serial converter 310 carries out a parallel toserial conversion of the received frequency inversely-spread signal.Last, the data deciding section 311 decides about the data of theconverted signal, and demodulates the data.

[0023] However, the above conventional mobile communication system hasthe following problems.

[0024] For example, according to the conventional mobile communicationsystem, multi-path waves passing through a plurality of transmissionlines arrive at a mobile station, as waves that are reflected,diffracted, and scattered by the surrounding buildings and topography.These multi-path waves interfere with each other, and the frequencyselective fading, that is a random fluctuation in the amplitude and thephase of the reception wave, occurs. Particularly, when the mobilestation moves at a high speed, the fluctuation due to the frequencyselective fading becomes at a high speed. Therefore, there has been aproblem that it is not possible to sufficiently estimate the amplitudefluctuation and the phase fluctuation due to the fading, and the qualityof the reception signal and the data demodulation precision aredegraded.

[0025] According to the conventional mobile communication system, themulticarrier CDMA receiving apparatus calculates the degraded receptionsignal quality, and the multicarrier CDMA transmitting apparatus usesthe degraded reception signal quality to control the transmission power.Therefore, there has been a problem that the communication quality isalso degraded.

[0026] According to the conventional mobile communication system, whenthe transmission signal from the base station receives the influence ofthe frequency selective fading on the transmission line, a plurality ofdelayed waves exist depending on the states of the transmission lines.Therefore, there has been a problem that it is difficult to calculatethe signal power already arrived at the mobile station as a criterion ofthe reception signal quality. Further, when the interference occurs dueto the multiple user signals, it has been difficult to estimate in highprecision the reception signal quality that takes into account this userinterference.

[0027] In the multimedia mobile communications, the transmittingapparatus needs to change the spread spectrum rate or multiple values ofthe modulation signal and adaptively change the information speedaccording to the handled application and the states of the transmissionlines. However, according to the conventional mobile communicationsystem, there has been a problem that it is not possible to estimate thereception signal quality in high precision because of level fluctuationssuch as fading and shadowing.

[0028] Therefore, the present invention has an object of providing amobile communication system, a multicarrier CDMA transmitting apparatus,and a multicarrier CDMA receiving apparatus that can realize ahigh-precision estimate processing of reception signal quality and asatisfactory data demodulation.

DISCLOSURE OF THE INVENTION

[0029] In the mobile communication system according to the presentinvention, a transmitting apparatus comprises a slot generating unit(corresponding to an S/P 201, slot generators 12-1 to 12-n, and copyingsections 212-1 to 212-n in embodiments to be described later) thatgenerates, for each subcarrier group unit, a slot consisting of a commonpilot portion, a known series portion which a receiving apparatus usesto estimate a signal to interference ratio, and a data portion, by usingtransmission data converted for each subcarrier group, copies each slotby a predetermined number of subcarriers, and outputs the slots, amodulating unit (corresponding to information modulators 213-1 to 213-n)that modulates the copied signal for each subcarrier unit within thesubcarrier group, a spread spectrum unit (corresponding to spreadspectrum sections 214-1 to 214-n) that individually spreads frequency ofa subcarrier signal within the modulated subcarrier group, atransmission power control unit (corresponding to transmission powervarying sections 13-1 to 13-n) that controls transmission power of thesubcarrier signal after the spread spectrum, for each subcarrier group,a multiplexing unit (corresponding to multiplexers 203-1 to 203-n) thatmultiplexes the subcarrier signal after the transmission power control,for each subcarrier group, and a transmitting unit (corresponding to aninverse Fourier transform calculator 204, a GI adder 205, a frequencyconverter 206, and an antenna 207) that generates a predetermined signalby carrying out an inverse Fourier transformation processing, a guardinterval setting processing, and a frequency conversion processing tothe multiplexed subcarrier signal, and transmits the generated signal toa transmission line, and the receiving apparatus comprises a receivingunit (corresponding to an antenna 301, a frequency converter 302, a GIremoving section 303, and a Fourier transform calculator 304) thatconverts the received signal on the transmission line into a basebandsignal, and carries out a Fourier transformation processing to thebaseband signal, a common pilot extracting unit (corresponding to commonpilot extractors 305-1 to 305-n) that extracts the common pilot portionincluded in each of the Fourier-transformed subcarrier signals, achannel estimating unit (corresponding to a by-subcarrier channelestimator 306) that calculates a channel estimate value for eachsubcarrier, by using the common pilot portion, a delay unit(corresponding to a delay unit 307) that delays each Fourier-transformedsubcarrier signal by a time required to carry out the extractionprocessing, and the channel estimate processing, a fading compensatingunit (corresponding to fading compensating sections 1-1 to 1-m) thatcarries out a fading compensation to each of the delayed subcarriersignals, by using each of the channel estimate values, an inverse spreadspectrum unit (corresponding to an inverse spread spectrum section 309)that inverse spreads frequency of each of the fading-compensatedsubcarrier signals, an SIR (signal to interference ratio) estimatingunit (corresponding to SIR calculators 2-1 to 2-n, a subcarrier groupaveraging section 3, and an averaging section 4) that estimates thesignal to interference ratio by using the known series portion includedin the subcarrier group signal after the inverse spread spectrum, and ademodulating unit (corresponding to a P/S 310, and a data decidingsection 311) that demodulates the subcarrier group signal after theinverse spread spectrum.

[0030] In the mobile communication system according to the nextinvention, the channel estimating unit first calculates a channelestimate value for one subcarrier, then calculates a linearinterpolation value between two slots by using the calculated channelestimate value of the subcarrier and a channel estimate value of asubcarrier calculated when the next slot is input, and outputs a resultof the calculation as a channel estimate value.

[0031] In the mobile communication system according to the nextinvention, the SIR estimating unit comprises: a known-series extractingunit that extracts the known series portion; a known-series generatingunit that generates a known series already known; an inverse modulatingunit that removes a modulation component of the known-series portion byutilizing the known series; a first averaging unit that suppresses anoise component by carrying out an in-phase averaging processing usingthe known series portion after the removal of the modulation-component;a first squaring unit that calculates signal power by squaring the knownseries portion after the averaging processing; a re-modulating unit thatcarries out a re-modulation processing by using the known series and theknown series portion after the averaging processing; a subtracting unitthat subtracts the re-modulated signal from the known series portionextracted by the known-series extracting unit; a second squaring unitthat squares the signal after the subtraction; a second averaging unitthat carries out an averaging processing of interference power by usinga signal output from the second squaring unit; a dividing unit thatdivides the signal power by the averaged interference power; asubcarrier group averaging unit that combines each result of thedivision obtained for each subcarrier group, and averages the combinedresult by dividing it with a number of subcarrier groups used for thecombining; and a slot averaging unit that averages the signals averagedusing the number of the subcarrier groups, over a plurality of slots.

[0032] In the mobile communication system according to the nextinvention, the SIR estimating unit comprises: a known-series extractingunit that extracts the known series portion; a known-series generatingunit that generates a known series already known; an inverse modulatingunit that removes a modulation component of the known-series portion byutilizing the known series; a first averaging unit that suppresses anoise component by carrying out an in-phase averaging processing usingthe known series portion after the removal of the modulation component;a first squaring unit that calculates signal power by squaring the knownseries portion after the averaging processing; a re-modulating unit thatcarries out a re-modulation processing by using the known series and theknown series portion after the averaging processing; a subtracting unitthat subtracts the re-modulated signal from the known series portionextracted by the known-series extracting unit; a second squaring unitthat squares the signal after the subtraction; a second averaging unitthat carries out an averaging processing of interference power by usinga signal output from the second squaring unit; a first slot averagingunit that averages the averaged interference power, over a plurality ofslots; a dividing unit that divides the signal power by the averagedinterference power obtained by averaging over the slots; a subcarriergroup averaging unit that combines each result of the division obtainedfor each subcarrier group, and averages the combined result by dividingit with a number of subcarrier groups used for the combining; and a slotaveraging unit that averages for a plurality of slots, the signalsaveraged using the number of the subcarrier groups.

[0033] In the mobile communication system according to the nextinvention, the SIR estimating unit makes the output of the subcarriergroup averaging unit as an estimate signal to interference ratio.

[0034] In the mobile communication system according to the nextinvention, the SIR estimating unit makes a result of the divisionobtained for each subcarrier group as an estimate signal to interferenceratio.

[0035] In the mobile communication system according to the nextinvention, the SIR estimating unit averages the result of the divisionobtained for each subcarrier group, over a plurality of slots for eachsubcarrier group, and makes a result of the averaging as an estimatesignal to interference ratio.

[0036] In the mobile communication system according to the nextinvention, the modulating unit selects any one of modulation systemsfrom among BPSK (Binary Phase Shift Keying), QPSK (Quadrature PhaseShift Keying), 8 PSK, 16 PSK, 16 QAM (Quadrature Amplitude Modulation),64 QAM, 128 QAM, and 256 QAM, according to the received signal tointerference ratio.

[0037] In the mobile communication system according to the nextinvention, the spread spectrum unit selects a suitable spread spectrumrate according to the received signal to interference ratio.

[0038] A multicarrier CDMA transmitting apparatus according to the nextinvention comprises: a slot generating unit that generates, for eachsubcarrier group unit, a slot consisting of a common pilot portion, aknown series portion which a receiving apparatus uses to estimate asignal to interference ratio, and a data portion, by using transmissiondata converted for each subcarrier group, copies each slot by apredetermined number of subcarriers, and outputs the slots; a modulatingunit that modulates the copied signal for each subcarrier unit withinthe subcarrier group; a spread spectrum unit that individually spreadsthe spectrum of a subcarrier signal within the modulated subcarriergroup; a transmission power control unit that controls transmissionpower of the subcarrier signal after the spread spectrum, for eachsubcarrier group; a multiplexing unit that multiplexes the subcarriersignal after the transmission power control, for each subcarrier group;and a transmitting unit that generates a predetermined signal bycarrying out an inverse Fourier transformation processing, a guardinterval setting processing, and a frequency conversion processing tothe multiplexed subcarrier signal, and transmits the generated signal toa transmission line.

[0039] In the multicarrier CDMA transmitting apparatus according to thenext invention, the modulating unit selects any one of modulationsystems from among BPSK, QPSK, 8 PSK, 16 PSK, 16 QAM, 64 QAM, 128 QAM,and 256 QAM, according to the received signal to interference ratio.

[0040] In the multicarrier CDMA transmitting apparatus according to thenext invention, the spread spectrum unit selects a suitable spreadspectrum rate according to the received signal to interference ratio.

[0041] A multicarrier CDMA receiving apparatus according to the nextinvention comprises: a receiving unit that converts the received signalon the transmission line into a baseband signal, and carries out aFourier transformation processing to the baseband signal; a common pilotextracting unit that extracts the common pilot portion included in eachof the Fourier-transformed subcarrier signals; a channel estimating unitthat calculates a channel estimate value for each subcarrier, by usingthe common pilot portion; a delay unit that delays eachFourier-transformed subcarrier signal by a time required to carry outthe extraction processing, and the channel estimate processing; a fadingcompensating unit that carries out a fading compensation to each of thedelayed subcarrier signals, by using each of the channel estimatevalues; an inverse spread spectrum unit that inverse spreads frequencyof each of the fading-compensated subcarrier signals; an SIR estimatingunit that estimates the signal to interference ratio by using the knownseries portion included in the subcarrier group signal after the inversespread spectrum; and a demodulating unit that demodulates the subcarriergroup signal after the inverse spread spectrum.

[0042] In the multicarrier CDMA receiving apparatus according to thenext invention, the channel estimating unit first calculates a channelestimate value for one subcarrier, then calculates a linearinterpolation value between two slots by using the calculated channelestimate value of the subcarrier and a channel estimate value of asubcarrier calculated when the next slot is input, and outputs a resultof the calculation as a channel estimate value.

[0043] In the multicarrier CDMA receiving apparatus according to thenext invention, the SIR estimating unit comprises: a known-seriesextracting unit that extracts the known series portion; a known-seriesgenerating unit that generates a known series already known; an inversemodulating unit that removes a modulation component of the known-seriesportion by utilizing the known series; a first averaging unit thatsuppresses a noise component by carrying out an in-phase averagingprocessing using the known series portion after the removal of themodulation component; a first squaring unit that calculates signal powerby squaring the known series portion after the averaging processing; are-modulating unit that carries out a re-modulation processing by usingthe known series and the known series portion after the averagingprocessing; a subtracting unit that subtracts the re-modulated signalfrom the known series portion extracted by the known-series extractingunit; a second squaring unit that squares the signal after thesubtraction; a second averaging unit that carries out an averagingprocessing of interference power by using a signal output from thesecond squaring unit; a dividing unit that divides the signal power bythe averaged interference power; a subcarrier group averaging unit thatcombines each result of the division obtained for each subcarrier group,and averages the combined result by dividing it with a number ofsubcarrier groups used for the combining; and a slot averaging unit thataverages the signals averaged using the number of the subcarrier groups,over a plurality of slots.

[0044] In the multicarrier CDMA receiving apparatus according to thenext invention, the SIR estimating unit comprises: a known-seriesextracting unit that extracts the known series portion; a known-seriesgenerating unit that generates a known series already known; an inversemodulating unit that removes a modulation component of the known-seriesportion by utilizing the known series; a first averaging unit thatsuppresses a noise component by carrying out an in-phase averagingprocessing using the known series portion after the removal of themodulation component; a first squaring unit that calculates signal powerby squaring the known series portion after the averaging processing; are-modulating unit that carries out a re-modulation processing by usingthe known series and the known series portion after the averagingprocessing; a subtracting unit that subtracts the re-modulated signalfrom the known series portion extracted by the known-series extractingunit; a second squaring unit that squares the signal after thesubtraction; a second averaging unit that carries out an averagingprocessing of interference power by using a signal output from thesecond squaring unit; a first slot averaging unit that averages theaveraged interference power, over a plurality of slots; a dividing unitthat divides the signal power by the averaged interference powerobtained by averaging over the slots; a subcarrier group averaging unitthat combines each result of the division obtained for each subcarriergroup, and averages the combined result by dividing it with a number ofsubcarrier groups used for the combining; and a slot averaging unit thataverages for a plurality of slots, the signals averaged using the numberof the subcarrier groups.

[0045] In the multicarrier CDMA receiving apparatus according to thenext invention, the SIR estimating unit makes the output of thesubcarrier group averaging unit as an estimate signal to interferenceratio.

[0046] In the multicarrier CDMA receiving apparatus according to thenext invention, the SIR estimating unit makes a result of the divisionobtained for each subcarrier group as an estimate signal to interferenceratio.

[0047] In the multicarrier CDMA receiving apparatus according to thenext invention, the SIR estimating unit averages the result of thedivision obtained for each subcarrier group, over a plurality of slotsfor each subcarrier group, and makes a result of the averaging as anestimate signal to interference ratio.

BRIEF DESCRIPTION OF THE DRAWINGS

[0048]FIG. 1 shows a structure of a receiving apparatus according to afirst embodiment of the present invention;

[0049]FIG. 2 shows a structure of a transmitting apparatus according tothe first embodiment;

[0050]FIG. 3 shows a structure of a slot generator;

[0051]FIG. 4 shows a slot format of a subcarrier;

[0052]FIG. 5 shows a structure of a transmission power varying section;

[0053]FIG. 6 shows a structure of a fading compensating section;

[0054]FIG. 7 shows a structure of SIR calculator;

[0055]FIG. 8 shows a structure of an averaging section 4;

[0056]FIG. 9 shows a structure of the averaging section 4;

[0057]FIG. 10 shows a structure of SIR calculator according to a secondembodiment;

[0058]FIG. 11 shows a structure of an information modulator according toa third embodiment;

[0059]FIG. 12 shows one example of changes of a modulation system;

[0060]FIG. 13 shows one example of changes of spread spectrum rates;

[0061]FIG. 14 shows a structure of a conventional multicarrier CDMAtransmitting apparatus;

[0062]FIG. 15 shows a structure of a conventional multicarrier CDMAreceiving apparatus;

[0063]FIG. 16 shows a frame format of a subcarrier;

[0064]FIG. 17 shows a structure of a copying section;

[0065]FIG. 18 shows a structure of an information modulator;

[0066]FIG. 19 shows a structure of a spread spectrum section;

[0067]FIG. 20 explains how guard intervals are added to the signals;

[0068]FIG. 21 shows one example of an impulse response of frequencyselective fading transmission lines;

[0069]FIG. 22 shows modulation signals on the frequency axis whenN_(scg) is equal to four and also when N_(sub) is equal to eight;

[0070]FIG. 23 shows a structure of fading compensating section; and

[0071]FIG. 24 shows a structure of an inverse spread spectrum section.

BEST MODE FOR CARRYING OUT THE INVENTION

[0072] The mobile communication system, the multicarrier CDMAtransmitting apparatus (hereinafter, “transmitting apparatus”), and themulticarrier CDMA receiving apparatus (hereinafter “receivingapparatus”) according to the embodiments of the present invention areexplained below with reference to the drawings. The present invention isnot limited by these embodiments.

[0073] First Embodiment

[0074]FIG. 1 shows a structure of the receiving apparatus according to afirst embodiment of the present invention. In FIG. 1, the referencenumeral 301 denotes the antenna, 302 denotes the frequency converter,303 denotes the guard interval remover, 304 denotes the Fouriertransform calculator, 305-1 to 305-m denote the common pilot extractorsrespectively, 306 denotes the by-subcarrier channel estimator, 307denotes the delay unit, 1-1, 1-2, 1-3, . . . , and 1-m denote fadingcompensating sections respectively, 309 denotes the inverse spreadspectrum section, 2-1, 2-2, 2-3, . . . , and 2-n denote SIR calculators,310 denotes the parallel to serial converter, 311 denotes the datadeciding section, 3 denotes a subcarrier group averaging section, and 4denotes an averaging section.

[0075]FIG. 2 shows a structure of the transmitting apparatus accordingto the first embodiment. In FIG. 2, the reference numeral 201 denotesthe serial to parallel converter (S/P), 11-1, 11-2, . . . , and 11-ndenote a first, a second, . . . , and a N_(scg) (=n)-th subcarrier groupmodulation processors respectively, 203-1, 203-2, . . . , and 203-ndenote the multiplexers respectively, 204 denotes the inverse Fouriertransform calculator, 205 denotes the guard interval (GI) adder, 206denotes the frequency converter, and 207 denotes the antenna. In eachsubcarrier group modulation processor, 12-1, 12-2, . . . , and 12-ndenote slot generators, 212-1, 212-2, . . . , and 212-n denote thecopying sections respectively, 213-1, 213-2, . . . , 213-n denote theinformation modulators respectively, 214-1, 214-2, . . . , and 214-ndenote the spread spectrum sections respectively, and 13-1, 13-2, . . ., and 13-n denote transmission power varying sections respectively.

[0076] The operation of the multicarrier CDMA transmitting and receivingapparatuses in the mobile communication system according to the presentembodiment is explained. Data transmission and reception between a basestation and a plurality of terminals is assumed.

[0077] First, the operation of the transmitting apparatus is explained.Transmission data to be transmitted to an optional terminal is input tothe serial to parallel converter 201, which converts the data intoparallel data so that the parallel number of the data becomes N_(scg)(that is, a predetermined integer). The parallel data reach thesubcarrier group modulation processors 11-1 to 11-n respectively. Eachof the first to the N_(scg)-th subcarrier group modulation processorscarries out the same signal processing of the modulation processing toeach subcarrier group. Therefore, the operation of the first subcarriergroup modulation processor 11-1 is explained here, and the explanationof the operation of the rest of the subcarrier group modulationprocessors is omitted.

[0078] Of the parallel data output from the serial to parallel converter201, the first data series is input to the subcarrier group modulationprocessor 11-1. The slot generator 12-1 prepares a predetermined slot.FIG. 3 shows in detail a structure of, for example, the slot generator12-1. A reference numeral 21 denotes a by-slot data divider, 22 denotesa known-series adder, and 23 denotes a common pilot adder. FIG. 4 showsa slot format for each subcarrier. Specifically, in the slot generator12-1, in order to generate the slot shown in FIG. 4, the by-slot datadivider 21 divides the data into N_(data) symbols as a slot data size.The known-series adder 22 receives the data after the data divisionprocessing, and adds known series of N_(kw) symbols set in advance, tothe data. The common pilot adder 23 receives the data added with theknown series, and adds known series of N_(pilot) symbols set in advance,to this data, thereby to finally prepare the subcarrier group data inthe slot structure shown in FIG. 4. The common pilot adder 23 outputsthe subcarrier group data to the copying section 212-1. Other slotdetectors have a structure similar to that of the slot detector 12-1.

[0079] The copying section 212-1 receives the first subcarrier groupdata, copies the frame by a predetermined number of subcarriers N_(sub)(=m), and prepares the N_(sub) subcarrier signals. The structure ofcopying section is similar to the one shown in FIG. 17. The copyingsection 212-1 outputs the N_(sub) subcarrier signals to the informationmodulator 213-1.

[0080] The information modulator 213-1 receives the N_(sub) subcarriersignals, and carries out QPSK modulation of the signals with the QPSKmodulators 221-1 to 221-m respectively, and prepares N_(sub)information-modulated subcarrier signals. The structure of informationmodulator is similar to the one shown in FIG. 18. The informationmodulator 213-1 outputs the N_(sub) information-modulated subcarriersignals to the spread spectrum section 214-1.

[0081] The spread spectrum section 214-1 spreads the spectrum of theN_(sub) information-modulated subcarrier signals respectively by usingmutually quadrate spread spectrum codes (which are expressed as ±1)given in advance in a plurality of terminals or other transmissionchannels. The structure of spread spectrum section is similar to the oneshown in FIG. 19. More specifically, the spread spectrum section 214-1multiplies the N_(sub) information-modulated subcarrier signals by eachspread spectrum code that is output from the spread spectrum codegenerator 222. For the spread spectrum codes, orthogonal codes of Walshcodes are generally used. The spread spectrum section 214-1 outputs theN_(sub) subcarrier signals after the spread spectrum to the transmissionpower varying section 13-1.

[0082]FIG. 5 shows in detail a structure of, for example, a transmissionpower varying section 13-1. Reference numerals 31-1, 31-2, . . . , and31-m denote multipliers. The transmission power varying section 13-1multiplies the N_(sub) subcarrier signals after the spread spectrum thatthe multipliers 31-1, 31-2, . . . , and 31-m received by transmissionpower control gains that correspond to these signals respectively, andgenerates transmission power-controlled subcarrier signals as results ofthe multiplication. The transmission power varying section 13-1 outputsthe transmission power-controlled subcarrier signals to the multiplexer203-1. For each transmission power control gain, a suitable value is setso that the receiving terminal can keep the signal quality at a constantlevel, based on the reception signal quality at the receiving terminal.Other transmission power varying sections have a structure similar tothat of the transmission power varying section 13-1.

[0083] The multiplexer 203-1 receives the N_(sub) transmissionpower-controlled subcarrier signals, multiplexes these subcarriersignals (that is, transmission signals to be transmitted to theterminals), and outputs the multiplexed subcarrier signals to theinverse Fourier transform calculator 204. At this time, the inverseFourier transform calculator 204 receives the inputs of all theN_(scg)×N_(sub) (=N_(c)) subcarrier signals, which includes themultiplexed subcarrier signals obtained from the multiplexers 203-2 to203-n, in addition to the input from the multiplexer 203-1. Othermultiplexer perform functions similar to that of the multiplexer 203-1.

[0084] The inverse Fourier transform calculator 204 calculates inverseFourier transform of the subcarrier signals received, and outputs theinverse Fourier-transformed signals to the guard interval adder 205.

[0085] The guard interval adder 205 copies the latter portions of thesymbols of the inverse Fourier-transformed signals corresponding to atime τ_(GI), and adds these portions to the headers of the symbols(refer to FIG. 20). The guard interval adder 205 outputs the guardinterval-added signals to the frequency converter 206. In general,τ_(GI) is set larger than the spread of delayed waves on thetransmission lines (refer to FIG. 21).

[0086] Finally, the frequency converter 206 carries out a predeterminedfrequency conversion processing to the received guard interval-addedsignals, and outputs the frequency-converted signals to the radiocommunication transmission lines via the antenna 207.

[0087] The operations of the receiving apparatus will be explained nextwith reference to FIG. 1. The frequency converter 302 receives, via theantenna 301, the signals influenced by the frequency selective fading onthe radio communication lines, and converts these signals into basebandsignals. The frequency converter 302 outputs the baseband signals to theguard interval remover 303.

[0088] The guard interval remover 303 removes the guard intervals (GI)from the received baseband signals, and generates the continuous signalsof symbols (refer to the upper portion in FIG. 20). The guard intervalremover 303 outputs the generated signals to the Fourier transformcalculator 304.

[0089] The Fourier transform calculator 304 calculates Fourier transformof the signals received, and generates N_(scg)×N_(sub) (=N_(c))subcarrier signals. The Fourier transform calculator 304 outputs eachsubcarrier signal of each subcarrier to the delay unit 307, and thecommon pilot extractors 305-1 to 305-m respectively.

[0090] The common pilot extractors 305-1 to 305-m extract common pilotportions from the received subcarrier signals respectively. Theby-subcarrier channel estimator 306 adds in-phase channel estimatevalues of adjacent three subcarriers, thereby to calculate a channelestimate value of each subcarrier after suppressing noise component. Theby-subcarrier channel estimator 306 outputs channel estimate values(that is, subcarrier channel estimate values) for each subcarrier to thefading compensating sections 1-1 to 1-m.

[0091] On the other hand, the delay unit 307 receives eachFourier-transformed subcarrier signal, and delays each signal to adjustdelays due to the processing in the common pilot extractors 305-1 to305-m and the processing in the by-subcarrier channel estimator 306. Thedelay unit 307 outputs the respective delayed subcarrier signals to thefading compensating sections 1-1 to 1-m.

[0092]FIG. 6 shows in detail a structure of, for example, the fadingcompensating section 1-1. A reference numeral 41 denotes an absolutevalue calculator, 42 denotes a divider, 43 denotes a complex conjugatenumber calculator, and 44 denotes a multiplier. The fading compensatingsection 1-1 normalizes the subcarrier channel estimate signals based ona signal amplitude in order to compensate for the phase component due tothe fading fluctuation. Specifically, the absolute value calculator 41calculates an absolute value of the received subcarrier channel estimatevalue in order to calculate the amplitude of this subcarrier channelestimate value. The divider 42 divides the received subcarrier channelestimate value by this absolute value to carry out the normalizationprocessing. The complex conjugate number calculator 43 receives theresult of the division, and calculates a complex conjugate number basedon the output from the divider 42. The multiplier 44 multiplies thereceived subcarrier signal by the calculated complex conjugate number.Last, the fading compensating section 1-1 outputs the fading-compensatedsubcarrier signal of each subcarrier to the inverse spread spectrumsection 309. Other fading compensating sections have a structure similarto that of the fading compensating section 1-1.

[0093] The inverse spread spectrum section 309 handles the N_(sub)subcarrier signals corresponding to each subcarrier group as one unit ofprocessing. Each of the multipliers 324-1 to 324-m receives the N_(sub)subcarrier signals, and multiplies the N_(sub) subcarrier signals by theinverse spread spectrum code (which is the same as the spread spectrumcode and which can be expressed as ±1) that is output from the inversespread spectrum code generator 323. The combiner 325 combines thereceived inversely-spread N_(sub) subcarrier signals, and generates aninverse spread spectrum signal corresponding to the subcarrier groupsignals as the result of the combining. The combiner 325 outputs thefrequency inverse spread signal, for each subcarrier group, to the SIRcalculators 2-1 to 2-n, and the parallel to serial converter 310.

[0094]FIG. 7 shows in detail a structure of, for example, the SIRcalculator 2-1. A reference numeral 51 denotes a known-series extractor,52 denotes an inverse modulator, 53 denotes an averaging section, 54denotes a squaring section, 55 denotes a known-series generator, 56denotes a re-modulator, 57 denotes a subtractor, 58 denotes a squaringsection, 59 denotes an averaging section, and 60 denotes a divider.Other SIR calculators have a structure similar to, and perform functionssimilar to, that of the SIR calculator 2-1, and therefore, only theoperations of the SIR calculator 2-1 will be explained below. In the SIRcalculator 2-1, first the known-series extractor 51 extracts the knownseries shown in FIG. 4 from among the frequency inversely-spreadsubcarrier group signals received.

[0095] The inverse modulator 52 receives the extracted known-seriesportion, and removes the modulation component by utilizing the knownseries known in advance at the receiving terminal that the known-seriesgenerator 55 generates. Next, the averaging section 53 receives theknown series portion after the removal of the modulation component, andcarries out the in-phase averaging by using the N_(kw) known-seriesportion symbols, thereby to suppress the noise component. Next, thesquaring section 54 receives the known series portion after theaveraging processing, and squares the known series portion.

[0096] On the other hand, the re-modulator 56 receives the known seriesthat the receiving apparatus knows in advance and that is generated bythe known series generator 55, and the known series portion after theaveraging processing that is output from the averaging section 53. There-modulator 56 carries out the modulation processing again by usingthese signals. In the present embodiment, the transmitting apparatusshown in FIG. 2 carries out the QPSK modulation as the informationmodulation. Therefore, the re-modulator 56 carries out the QPSKmodulation again.

[0097] The subtractor 57 subtracts the re-modulated signal from thereceived known series portion that the known series detector 51extracted. The subtractor 57 subtracts the signal by the number ofN_(kw) that corresponds to the number of known symbols, for each symbol.The squaring section 58 receives results of the subtraction, andcalculates squared values of the N_(kw) symbols. Next, the averagingsection 59 averages the received squared results, thereby to obtainaverage interference power of the N_(kw) symbols.

[0098] Finally, the divider 60 in the SIR calculator 2-1 divides thecalculation result of the squaring section 54 by the calculation resultof the averaging section 59, thereby to generate the SIR calculationvalue of the subcarrier group for each slot. The divider 60 outputs theSIR calculation value to the subcarrier group averaging section 3.

[0099] Referring back to FIG. 1, the subcarrier group averaging section3 receives the SIR calculation values from all the SIR calculators 2-1to 2-n, averages the N_(scg) SIR calculation values, and outputs theaveraged result to the averaging section 4.

[0100]FIG. 8 shows in detail a structure of the averaging section 4. Areference numeral 71 denotes an amplifier, 72 denotes an adder, 73denotes an amplifier, and 74 denotes a delay unit. In the averagingsection 4, the amplifier 71 first multiplies the received combinationresult by an arbitrary a (0<α<1) as a gain. Next, the adder 72 adds aresult of the calculation by the amplifier 73 and a result of thecalculation by the amplifier 71, and outputs a result of this additionas an averaged SIR estimate value. The delay unit 74 receives theaveraged SIR estimate value, and delays this value by a constant periodof time, such as by one slot component, for example. The amplifier 73multiplies the delayed SIR estimate value by the gain (1−α), and outputsa result of this addition to the adder 72.

[0101] In the present embodiment, while the structure shown in FIG. 8 isused as an example of the averaging section 4, the structure is notlimited to this. It is also possible to use an averaging section asshown in FIG. 9, for example. In FIG. 9, a reference numeral 75 denotesa shift register, 76 denotes an adder, and 77 denotes a divider thatdivides the result of the addition by an arbitrary M. When the structureshown in FIG. 9 is used, in the averaging section 4, the shift register75 first receives the combined SIR calculation value, and shifts this byeach slot. Next, the adder 76 adds the SIR values of the M slots. Last,the divider 77 divides a result of this addition by M, thereby to obtainan average SIR calculation value of the M slots.

[0102] As explained above, in the present embodiment, the common pilotsymbol and the known series are added to each slot of the subcarriergroup. Therefore, it is possible to obtain a high-precision SIRcalculation value for each subcarrier group.

[0103] In the present embodiment, after the SIR calculation valuesobtained for each subcarrier group are combined together, the SIRcalculation values are averaged. Therefore, it is possible to obtain ahigh-precision SIR calculation value, even when there is a levelfluctuation such as shadowing.

[0104] In the present embodiment, based on a result of the combining ofthe SIR calculation values obtained for each subcarrier group, thetransmitting apparatus controls the transmission power. Therefore, thereceiving apparatus can obtain high-precision reception signal quality.

[0105] In the present embodiment, the known series are disposed afterthe common pilot symbol, in each slot. However, it is not alwaysnecessary to dispose the known series after the common pilot symbol, andit is also possible to dispose the known series in the middle of theslot or at the end of the slot.

[0106] The by-subcarrier channel estimator 306 may calculate a linearinterpolation value between two slots, by using anoise-component-suppressed channel estimate value of a subcarrier thatis calculated first, and a channel estimate value of a subcarriersimilarly calculated when the next slot is input.

[0107] Assume that the by-subcarrier channel estimate value of thecurrent slot is expressed as C (0), that the by-subcarrier channelestimate value of the next slot is expressed as C (1), and that thenumber of symbols between the common pilot symbols is expressed as(N_(kw)+N_(data)) (refer to FIG. 4). Then, it is possible to express achannel estimate value “cir (k)” of the (N_(kw)+N_(data)) symbols of theknown series portions and the data portions within the slots, asfollows: $\begin{matrix}{{{{cir}\quad (k)} = {{{C(0)}{Q_{0}( {k/( {N_{kw} + N_{data}} )} )}} + {{C(1)}{Q_{1}( {k/( {N_{kw} + N_{data}} )} )}}}},} & (1)\end{matrix}$

[0108] where k=0, 1, 2, . . . , and (N_(kw)+N_(data)−1). It is possibleto express Q₀ and Q₁ by the following equations (2) and (3)respectively.

Q ₀ (k/(N _(kw) +N _(data)))=1−k/(N _(kw) +N _(data))  (2)

Q1₀ (k/(N _(kw) +N _(data)))=k/(N _(kw) +N _(data))  (3)

[0109] The by-subcarrier channel estimate values calculated as explainedabove are output to the fading compensating sections 1-1 to 1-mrespectively. The fading compensating sections 1-1 to 1-m carry out thefading compensation. The delay unit 307 sets a delay quantity by takinginto account the above linear interpolation processing.

[0110] As the by-subcarrier channel estimator 306 carries out the linearinterpolation by using the common pilots of two slots for eachsubcarrier, it is possible to estimate a channel in high precision, evenwhen there occurs a high-speed fading fluctuation that cannot bedisregarded within the slots. Therefore, it is possible to carry out ahigh-precision fading compensation in the symbols of the known-seriesportion and the data portion. As a result, the precision of the SIRestimate value improves.

[0111] Second Embodiment

[0112] In the mobile communication system according to a secondembodiment, the SIR calculating method of the SIR calculator within thereceiving apparatus is different from the SIR calculating methodaccording to the first embodiment. Only the portions that operatedifferently from those in the first embodiment will be explained below.The transmitting apparatus and the receiving apparatus according to thesecond embodiment have similar structures to those shown in FIG. 1 andFIG. 2 respectively.

[0113]FIG. 10 shows a structure of SIR calculator according to thesecond embodiment. A reference numeral 61 denotes an averaging section.The averaging section 61 is input with average interference power foreach slot output from the averaging section 59. The averaging section 61further averages the average interference power by using a plurality ofslots. The structure of the averaging section 61 is the same as thatshown in FIG. 8 or FIG. 9.

[0114] Even in the present embodiment, it is possible to obtain theeffects similar to those obtained in the first embodiment. Afterestimating the average interference power for each slot, the SIRcalculating section further carries out the averaging processing byusing a plurality of slots, thereby to calculate interference power.Therefore, it is possible to calculate in higher precision the SIRestimate value as the criterion of the reception signal quality.

[0115] In the present embodiment, while the output from the averagingsection 4 is the SIR estimate value as shown in FIG. 1, the output isnot limited to this. For example, the output from the subcarrier groupaveraging section 3 may be the SIR estimate value. With thisarrangement, even when the signal power varies due to the fadingfluctuation, it is possible to calculate the SIR estimate value in highprecision by taking into account the fading fluctuation.

[0116] The outputs from the SIR calculators 2-1 to 2-n for eachsubcarrier group may be the SIR estimate values. In this case, the basestation can control the transmission power for each subcarrier groupbased on the SIR information received for each subcarrier group.

[0117] The averaging section 4 shown in FIG. 8 or FIG. 9 may beindividually provided at the latter stage of each of the SIR calculators2-1 to 2-n for each subcarrier group, so that the output value from eachaveraging section may be the SIR estimate value. In this case, it ispossible to control the transmission power for each subcarrier group,based on the SIR information for each subcarrier group by taking intoaccount the fading fluctuation.

[0118] Third Embodiment

[0119] In the mobile communication system according to a thirdembodiment, the operation of an information modulator within thetransmitting apparatus is different from that according to the first orthe second embodiment. Only the portions that operate differently fromthose in the first or the second embodiments will be explained below.The transmitting apparatus and the receiving apparatus according to thethird embodiment have similar structures to those shown in FIG. 1 andFIG. 2 respectively.

[0120]FIG. 11 shows a structure of the information modulator accordingto the third embodiment. Reference numerals 81-1, 81-2, . . . , and 81-mdenote multi-value modulators. Each information modulator receivesN_(sub) subcarrier signals. Then, the multi-value modulators 81-1, 81-2,. . . , and 81-m multi-value modulate these signals, and generateN_(sub) subcarrier signals after the information modulation. Themulti-value modulation includes modulation systems that make it possibleto transmit at least one bit per one symbol, such as BPSK, QPSK, 8 PSK,16 PSK, 16 QAM, 64 QAM, 128 QAM, and 256 QAM.

[0121] The operation of the above mobile communication system isexplained in detail below. First, the mobile station receiving apparatusestimates the SIR as the reception signal quality. The mobile stationtransmitting apparatus inserts the estimate result into the transmissionslot, and transmits the transmission slot to the base station. The basestation transmitting apparatus selects a suitable modulation systembased on the received SIR information, and thereafter transmits the databased on the selected modulation system.

[0122] The common pilot portion and the known-series portion of thetransmission slot that the base station transmits are modulated based ona predetermined modulation system. For example, the QPSK modulationsystem is used for this. For modulating the data portion, any one of themulti-value modulation systems BPSK, QPSK, 8 PSK, 16 PSK, 16 QAM, 64QAM, 128 QAM, and 256 QAM is used. When the number before the PSK of themodulation system is larger, it is possible to transmit a larger numberof bits per one symbol. However, the SIR as the reception signal qualityrequires a large value in order to satisfy the required reception signalquality. Therefore, the base station changes the modulation system basedon the SIR estimate value of the mobile station. FIG. 12 shows oneexample of changes of a modulation system. There is a possibility that aslight error occurs in the SIR estimate value depending on the states ofthe transmission lines. Therefore, an overlapping area is provided inthe SIR estimate value.

[0123] In the present embodiment, it is possible to obtain similareffects to those obtained from the first or the second embodiment.Further, the base station can change the information speed according tothe reception SIR from the mobile station. Therefore, it is possible tosubstantially improve the frequency utilization efficiency.

[0124] Fourth Embodiment

[0125] In the mobile communication system according to the fourthembodiment, the operation of the spread spectrum section within thetransmitting apparatus is different from that according to the first,the second, or the third embodiment. Only the portions that operatedifferently from those in the first, the second, or the thirdembodiments will be explained below. The transmitting apparatus and thereceiving apparatus according to the fourth embodiment have similarstructures to those shown in FIG. 1 and FIG. 2 respectively.

[0126] In the present embodiment, each spread spectrum section spreadsthe spectrum of the N_(sub) information-modulated subcarrier signals, byusing mutually orthogonal spread spectrum codes, like in the firstembodiment. More specifically, the spread spectrum section multipliesthe N_(sub) information-modulated subcarrier signals by each spreadspectrum code that is output from the spread spectrum code generator 222(refer to FIG. 19).

[0127] In the present embodiment, the spread spectrum rates that thespread spectrum sections 214-1 to 214-n of the base station transmittingapparatus use are set based on the SIR estimate values that the mobilestation receiving apparatus estimates.

[0128] In other words, in the present embodiment, the mobile stationreceiving apparatus estimates the SIR as the reception signal quality.The mobile station transmitting apparatus inserts the estimate resultinto the transmission slot, and transmits the transmission slot to thebase station. The base station transmitting apparatus selects a suitablespread spectrum rate based on the received SIR information, andthereafter, carries out the spread spectrum by using the selected spreadspectrum rate, and transmits the data.

[0129] The base station transmitting apparatus spreads the spectrum ofthe signal of the known-series portion of the transmission slot, basedon a spread spectrum rate determined in advance. The spread spectrumbecomes the basis for the receiving apparatus to estimate the SIR. It ispossible to use 1, 2, 4, 8, 16, 32, and the like, for the spreadspectrum rate of the data portion. As the spread spectrum rate becomeslarger, the frequency diversity effect becomes larger. When the lowinformation transmission speed is increased by making the informationspreading rate smaller, the SIR as the reception signal quality requiresa large value in order to satisfy the required quality. Therefore, thebase station can change the spread spectrum rate based on the SIRestimate value of the mobile station. FIG. 13 shows one example ofchanges of spread spectrum rates. There is a possibility that a slighterror occurs in the SIR estimate value depending on the states of thetransmission lines. Therefore, an overlapping area is provided in theSIR estimate value.

[0130] As explained above, in the present embodiment, it is possible toobtain similar effects to those obtained from the first to the thirdembodiments. Further, the base station can change the spread spectrumrate according to the reception SIR from the mobile station.

[0131] As explained above, according to the present invention, thecommon pilot symbol and the known series are added to each slot of thesubcarrier group. Therefore, there is an effect that it is possible toobtain a high-precision SIR calculation value for each subcarrier group.Further, based on a result of the combining of the SIR calculationvalues obtained for each subcarrier group, the transmitting apparatuscontrols the transmission power. Therefore, there is an effect that thereceiving apparatus can obtain high-precision reception signal quality.

[0132] According to the next invention, as the linear interpolation iscarried out using the common pilots of two slots for each subcarrier, itis possible to estimate a channel in high precision, even when thereoccurs a high-speed fading fluctuation that cannot be disregarded withinthe slots. Therefore, it is possible to carry out a high-precisionfading compensation in the symbols of the known-series portion and thedata portion. As a result, there is an effect that the precision of theSIR estimate value improves.

[0133] According to the next invention, after the SIR calculation valuesobtained for each subcarrier group are combined together, the SIRcalculation values are averaged. Therefore, there is an effect that t ispossible to obtain a high-precision SIR calculation value, even whenthere is a level fluctuation such as shadowing.

[0134] According to the next invention, after the average interferencepower for each slot is estimated, the averaging processing is furthercarried out using a plurality of slots, thereby to calculateinterference power. Therefore, there is an effect that it is possible tocalculate in higher precision the SIR estimate value as the criterion ofthe reception signal quality.

[0135] According to the next invention, even when the signal powervaries due to the fading fluctuation, there is an effect that it ispossible to calculate the SIR estimate value in high precision by takinginto account the fading fluctuation.

[0136] According to the next invention, there is an effect that the basestation can control the transmission power for each subcarrier groupbased on the SIR information received for each subcarrier group.

[0137] According to the next invention, there is an effect that it ispossible to control the transmission power for each subcarrier groupbased on the SIR information for each subcarrier group by taking intoaccount the fading fluctuation.

[0138] According to the next invention, the base station can change theinformation speed according to the reception SIR from the mobilestation. Therefore, there is an effect that it is possible tosubstantially improve the frequency utilization efficiency.

[0139] According to the next invention, there is an effect that the basestation can change the spread spectrum rate according to the receptionSIR from the mobile station.

[0140] According to the next invention, the common pilot symbol and theknown series are added to each slot of the subcarrier group. Therefore,there is an effect that the receiving apparatus can obtain ahigh-precision SIR calculation value for each subcarrier group. Further,based on a result of the combining of the SIR calculation valuesobtained for each subcarrier group, the transmitting apparatus controlsthe transmission power. Therefore, there is an effect that the receivingapparatus can obtain high-precision reception signal quality.

[0141] According to the next invention, the base station can change theinformation speed according to the reception SIR from the mobilestation. Therefore, there is an effect that it is possible tosubstantially improve the frequency utilization efficiency.

[0142] According to the next invention, there is an effect that the basestation can change the spread spectrum rate according to the receptionSIR from the mobile station.

[0143] According to the next invention, based on a result of thecombining of the SIR calculation values obtained for each subcarriergroup, the transmitting apparatus controls the transmission power.Therefore, there is an effect that the receiving apparatus can obtainhigh-precision reception signal quality.

[0144] According to the next invention, as the linear interpolation iscarried out using the common pilots of two slots for each subcarrier, itis possible to estimate a channel in high precision, even when thereoccurs a high-speed fading fluctuation that cannot be disregarded withinthe slots. Therefore, it is possible to carry out a high-precisionfading compensation in the symbols of the known-series portion and thedata portion. As a result, there is an effect that the precision of theSIR estimate value improves.

[0145] According to the next invention, after the SIR calculation valuesobtained for each subcarrier group are combined together, the SIRcalculation values are averaged. Therefore, there is an effect that t ispossible to obtain a high-precision SIR calculation value, even whenthere is a level fluctuation such as shadowing.

[0146] According to the next invention, after the average interferencepower for each slot is estimated, the averaging processing is furthercarried out using a plurality of slots, thereby to calculateinterference power. Therefore, there is an effect that it is possible tocalculate in higher precision the SIR estimate value as the criterion ofthe reception signal quality.

[0147] According to the next invention, even when the signal powervaries due to the fading fluctuation, there is an effect that it ispossible to calculate the SIR estimate value in high precision by takinginto account the fading fluctuation.

[0148] According to the next invention, there is an effect that the basestation can control the transmission power for each subcarrier groupbased on the SIR information received for each subcarrier group.

[0149] According to the next invention, there is an effect that it ispossible to control the transmission power for each subcarrier groupbased on the SIR information for each subcarrier group by taking intoaccount the fading fluctuation.

INDUSTRIAL APPLICABILITY

[0150] As explained above, the mobile communication system, themulticarrier CDMA transmitting apparatus, and the multicarrier CDMAreceiving apparatus according to the present invention are suitable foruse on the frequency selective fading transmission lines.

1. A mobile communication system, which employs a multicarrier codedivision multiple access, comprising a transmitting apparatus and areceiving apparatus, the transmitting apparatus having a slot generatingunit that generates, for each subcarrier group unit, a slot consistingof a common pilot portion, a known series portion which the receivingapparatus uses to estimate a signal to interference ratio, and a dataportion, by using transmission data converted for each subcarrier group,copies each slot by a predetermined number of subcarriers, and outputsthe slots; a modulating unit that modulates the signal copied for eachsubcarrier unit within the subcarrier group; a spread spectrum unit thatindividually carries out frequency spreading to a subcarrier signalwithin the modulated subcarrier group; a transmission power control unitthat controls transmission power of the subcarrier signal after thespread spectrum, for each subcarrier group; a multiplexing unit thatmultiplexes the subcarrier signal after the transmission power control,for each subcarrier group; and a transmitting unit that generates apredetermined signal by carrying out an inverse Fourier transformationprocessing, a guard interval setting processing, and a frequencyconversion processing to the multiplexed subcarrier signal, andtransmits the signal generated to a transmission line, and the receivingapparatus having a receiving unit that receives a signal via on thetransmission line, converts the signal received into a baseband signal,and carries out a Fourier transformation processing to the basebandsignal; a common pilot extracting unit that extracts the common pilotportion included in each of the Fourier-transformed subcarrier signals;a channel estimating unit that calculates a channel estimate value foreach subcarrier, by using the common pilot portion; a delay unit thatdelays each Fourier-transformed subcarrier signal by a time required tocarry out the extraction processing, and the channel estimateprocessing; a fading compensating unit that carries out a fadingcompensation to each of the delayed subcarrier signals, by using each ofthe channel estimate values; an inverse spread spectrum unit thatinverse spreads frequency of each of the fading-compensated subcarriersignals; an SIR estimating unit that estimates a signal-to-interferenceratio by using the known series portion included in the subcarrier groupsignal after the inverse spread spectrum; and a demodulating unit thatdemodulates the subcarrier group signal after the inverse spreadspectrum.
 2. The mobile communication system according to claim 1,wherein the channel estimating unit first calculates a channel estimatevalue for one subcarrier, then calculates a linear interpolation valuebetween two slots by using the calculated channel estimate value of thesubcarrier and a channel estimate value of a subcarrier calculated whenthe next slot is input, and outputs a result of the calculation as achannel estimate value.
 3. The mobile communication system according toclaim 1, wherein the SIRSIR estimating unit comprises: a known-seriesextracting unit that extracts the known series portion; a known-seriesgenerating unit that generates a known series already known; an inversemodulating unit that removes a modulation component of the known-seriesportion by utilizing the known series; a first averaging unit thatsuppresses a noise component by carrying out an in-phase averagingprocessing using the known series portion after the removal of themodulation component; a first squaring unit that calculates signal powerby squaring the known series portion after the averaging processing; are-modulating unit that carries out a re-modulation processing by usingthe known series and the known series portion after the averagingprocessing; a subtracting unit that subtracts the re-modulated signalfrom the known series portion extracted by the known-series extractingunit; a second squaring unit that squares the signal after thesubtraction; a second averaging unit that carries out an averagingprocessing of interference power by using a signal output from thesecond squaring unit; a dividing unit that divides the signal power bythe averaged interference power; a subcarrier group averaging unit thatcombines each result of the division obtained for each subcarrier group,and averages the combined result by dividing it with a number ofsubcarrier groups used for the combining; and a slot averaging unit thataverages the signals averaged using the number of the subcarrier groups,over a plurality of slots.
 4. The mobile communication system accordingto claim 3, wherein the SIR estimating unit makes the output of thesubcarrier group averaging unit as an estimate signal to interferenceratio.
 5. The mobile communication system according to claim 3, whereinthe SIR estimating unit makes a result of the division obtained for eachsubcarrier group as an estimate signal to interference ratio.
 6. Themobile communication system according to claim 5, wherein the SIRestimating unit averages the result of the division obtained for eachsubcarrier group, over a plurality of slots for each subcarrier group,and makes a result of the averaging as an estimate signal tointerference ratio.
 7. The mobile communication system according toclaim 1, wherein the SIR estimating unit comprises: a known-seriesextracting unit that extracts the known series portion; a known-seriesgenerating unit that generates a known series already known; an inversemodulating unit that removes a modulation component of the known-seriesportion by utilizing the known series; a first averaging unit thatsuppresses a noise component by carrying out an in-phase averagingprocessing using the known series portion after the removal of themodulation component; a first squaring unit that calculates signal powerby squaring the known series portion after the averaging processing; are-modulating unit that carries out a re-modulation processing by usingthe known series and the known series portion after the averagingprocessing; a subtracting unit that subtracts the re-modulated signalfrom the known series portion extracted by the known-series extractingunit; a second squaring unit that squares the signal after thesubtraction; a second averaging unit that carries out an averagingprocessing of interference power by using a signal output from thesecond squaring unit; a first slot averaging unit that averages theaveraged interference power, over a plurality of slots; a dividing unitthat divides the signal power by the averaged interference powerobtained by averaging over the slots; a subcarrier group averaging unitthat combines each result of the division obtained for each subcarriergroup, and averages the combined result by dividing it with a number ofsubcarrier groups used for the combining; and a slot averaging unit thataverages for a plurality of slots, the signals averaged using the numberof the subcarrier groups.
 8. The mobile communication system accordingto claim 7, wherein the SIR estimating unit makes the output of thesubcarrier group averaging unit as an estimate signal to interferenceratio.
 9. The mobile communication system according to claim 7, whereinthe SIR estimating unit makes a result of the division obtained for eachsubcarrier group as an estimate signal to interference ratio.
 10. Themobile communication system according to claim 9, wherein the SIRestimating unit averages the result of the division obtained for eachsubcarrier group, over a plurality of slots for each subcarrier group,and makes a result of the averaging as an estimate signal tointerference ratio.
 11. The mobile communication system according toclaim 1, wherein the modulating unit selects any one of modulationsystems from among BPSK, QPSK, 8 PSK, 16 PSK, 16 QAM, 64 QAM, 128 QAM,and 256 QAM, according to the received signal to interference ratio. 12.The mobile communication system according to claim 1, wherein the spreadspectrum unit selects a suitable spread spectrum rate according to thereceived signal to interference ratio.
 13. A multicarrier code divisionmultiple access transmitting apparatus comprising: a slot generatingunit that generates, for each subcarrier group unit, a slot consistingof a common pilot portion, a known series portion which a receivingapparatus uses to estimate a signal to interference ratio, and a dataportion, by using transmission data converted for each subcarrier group,copies each slot by a predetermined number of subcarriers, and outputsthe slots; a modulating unit that modulates the copied signal for eachsubcarrier unit within the subcarrier group; a spread spectrum unit thatfrequency spreads a spectrum of each of subcarrier signals within themodulated subcarrier group; a transmission power control unit thatcontrols transmission power of the subcarrier signal after the spreadspectrum, for each subcarrier group; a multiplexing unit thatmultiplexes the subcarrier signal after the transmission power control,for each subcarrier group; and a transmitting unit that generates apredetermined signal by carrying out an inverse Fourier transformationprocessing, a guard interval setting processing, and a frequencyconversion processing to the multiplexed subcarrier signal, andtransmits the generated signal to a transmission line.
 14. Themulticarrier code division multiple access transmitting apparatusaccording to claim 13, wherein the modulating unit selects any one ofmodulation systems from among BPSK, QPSK, 8 PSK, 16 PSK, 16 QAM, 64 QAM,128 QAM, and 256 QAM, according to the received signal to interferenceratio.
 15. The multicarrier code division multiple access transmittingapparatus according to claim 13, wherein the spread spectrum unitselects a suitable spread spectrum rate according to the received signalto interference ratio.
 16. A multicarrier code division multiple accessreceiving apparatus comprising: a receiving unit that converts thereceived signal on the transmission line into a baseband signal, andcarries out a Fourier transformation processing to the baseband signal;a common pilot extracting unit that extracts the common pilot portionincluded in each of the Fourier-transformed subcarrier signals; achannel estimating unit that calculates a channel estimate value foreach subcarrier, by using the common pilot portion; a delay unit thatdelays each Fourier-transformed subcarrier signal by a time required tocarry out the extraction processing, and the channel estimateprocessing; a fading compensating unit that carries out a fadingcompensation to each of the delayed subcarrier signals, by using each ofthe channel estimate values; an inverse spread spectrum unit thatinverse spreads frequency of each of the fading-compensated subcarriersignals; a SIR estimating unit that estimates the signal to interferenceratio by using the known series portion included in the subcarrier groupsignal after the inverse spread spectrum; and a demodulating unit thatdemodulates the subcarrier group signal after the inverse spreadspectrum.
 17. The multicarrier code division multiple access receivingapparatus according to claim 16, wherein the channel estimating unitfirst calculates a channel estimate value for one subcarrier, thencalculates a linear interpolation value between two slots by using thecalculated channel estimate value of the subcarrier and a channelestimate value of a subcarrier calculated when the next slot is input,and outputs a result of the calculation as a channel estimate value. 18.The multicarrier code division multiple access receiving apparatusaccording to claim 16, wherein the SIR estimating unit comprises: aknown-series extracting unit that extracts the known series portion; aknown-series generating unit that generates a known series alreadyknown; an inverse modulating unit that removes a modulation component ofthe known-series portion by utilizing the known series; a firstaveraging unit that suppresses a noise component by carrying out anin-phase averaging processing using the known series portion after theremoval of the modulation component; a first squaring unit thatcalculates signal power by squaring the known series portion after theaveraging processing; a re-modulating unit that carries out are-modulation processing by using the known series and the known seriesportion after the averaging processing; a subtracting unit thatsubtracts the re-modulated signal from the known series portionextracted by the known-series extracting unit; a second squaring unitthat squares the signal after the subtraction; a second averaging unitthat carries out an averaging processing of interference power by usinga signal output from the second squaring unit; a dividing unit thatdivides the signal power by the averaged interference power; asubcarrier group averaging unit that combines each result of thedivision obtained for each subcarrier group, and averages the combinedresult by dividing it with a number of subcarrier groups used for thecombining; and a slot averaging unit that averages the signals averagedusing the number of the subcarrier groups, over a plurality of slots.19. The multicarrier code division multiple access receiving apparatusaccording to claim 18, wherein the SIR estimating unit makes the outputof the subcarrier group averaging unit as an estimate signal tointerference ratio.
 20. The multicarrier code division multiple accessreceiving apparatus according to claim 18, wherein the SIR estimatingunit makes a result of the division obtained for each subcarrier groupas an estimate signal to interference ratio.
 21. The multicarrier codedivision multiple access receiving apparatus according to claim 20,wherein the SIR estimating unit averages the result of the divisionobtained for each subcarrier group, over a plurality of slots for eachsubcarrier group, and makes a result of the averaging as an estimatesignal to interference ratio.
 22. The multicarrier code divisionmultiple access receiving apparatus according to claim 16, wherein theSIR estimating unit comprises: a known-series extracting unit thatextracts the known series portion; a known-series generating unit thatgenerates a known series already known; an inverse modulating unit thatremoves a modulation component of the known-series portion by utilizingthe known series; a first averaging unit that suppresses a noisecomponent by carrying out an in-phase averaging processing using theknown series portion after the removal of the modulation component; afirst squaring unit that calculates signal power by squaring the knownseries portion after the averaging processing; a re-modulating unit thatcarries out a re-modulation processing by using the known series and theknown series portion after the averaging processing; a subtracting unitthat subtracts the re-modulated signal from the known series portionextracted by the known-series extracting unit; a second squaring unitthat squares the signal after the subtraction; a second averaging unitthat carries out an averaging processing of interference power by usinga signal output from the second squaring unit; a first slot averagingunit that averages the averaged interference power, over a plurality ofslots; a dividing unit that divides the signal power by the averagedinterference power obtained by averaging over the slots; a subcarriergroup averaging unit that combines each result of the division obtainedfor each subcarrier group, and averages the combined result by dividingit with a number of subcarrier groups used for the combining; and a slotaveraging unit that averages for a plurality of slots, the signalsaveraged using the number of the subcarrier groups.
 23. The multicarriercode division multiple access receiving apparatus according to claim 22,wherein the SIR estimating unit makes the output of the subcarrier groupaveraging unit as an estimate signal to interference ratio.
 24. Themulticarrier code division multiple access receiving apparatus accordingto claim 22, wherein the SIR estimating unit makes a result of thedivision obtained for each subcarrier group as an estimate signal tointerference ratio.
 25. The multicarrier code division multiple accessreceiving apparatus according to claim 24, wherein the SIR estimatingunit averages the result of the division obtained for each subcarriergroup, over a plurality of slots for each subcarrier group, and makes aresult of the averaging as an estimate signal to interference ratio.